Thursday 25 November 2010 08.57 EST
First published on Thursday 25 November 2010 08.57 EST

Student groups have moved swiftly to capitalise on a growing movement against tuition fees, announcing another round of marches and walkouts after tens of thousands took part in a widespread day of action around Britain yesterday.

As London's chief police officer defended the tactic of "kettling" thousands of young demonstrators, the National Campaign Against Fees and Cuts (NCAFC), one of the umbrella groups organising the campaign, said it hopedmore students and pupils would protest next Tuesday.

There are also plans for a national day of action when the tuition fees bill is debated in parliament, likely to be next month.

The biggest event yesterday took place near Parliament Square in central London, where a crowd estimated at 5,000, including many school-age children, was penned in by police and not allowed to leave for some hours, a controversial tactic known as "kettling".

The Metropolitan police commissioner, Sir Paul Stephenson, insisted that the tactic – which police called "containment" – had been necessary because of criminal incidents including the vandalism of a police van by a handful of marchers.

Pressed by MPA members on why it took so long to release a crowd containing so many children, he answered: "Our job is to facilitate peaceful protests. But we have to get the message out that when it goes beyond the peaceful that it is criminal. It is quite clear that criminal acts took place."

But NCAFC, which is hoping to enlist trade union support for its upcoming actions, criticised the kettling.

"The actions of the Metropolitan Police yesterday were absolutely outrageous," a NCAFC spokesman, Simon Hardy, told a press conference. "Children as young as 13, 14, or 15 were not allowed to leave and were intimidated by hundreds upon hundreds of riot police and treated very badly when all they were doing was exercising their democratic right to protest."

Critics of kettling complain that being forcibly kept in a small area for some hours can inflame protesters' tempers, a point borne out after some of those eventually released from the London cordons smashed windows and hurled objects near Trafalgar Square. Police charged the 1,000-strong group on horseback. Over the course of the day two police officers and 15 people were injured in London, with 32 arrests made.

There were also big marches in Manchester, Liverpool, Sheffield, Leeds, Brighton and Cambridge and smaller protests and walkouts in many other places. The action was so disparate it was extremely difficult to gauge the total numbers involved, with estimates ranging from about 50,000 to more than 130,000. More than a dozen occupations and sit-ins were still continuing.

Another group remained in the Radcliffe Camera, an ornate, circular 18th-century building in Oxford now used as a university library. Charlotte, an architecture student who preferred not to give her full name, said the occupants did not know how long they would remain: "When the time comes for us to consider leaving, we'll do so in coordination with other occupations around the country," she said.